I. Field of the Invention
This invention relates to methods for producing fertilizers from low plant nutrient-containing organic materials and, more particularly, to methods for producing liquid, slurry or suspension fertilizers from such materials.
Organic materials and wastes, such as animal manure, sewage sludge, industrial organic waste and the like, have been used as fertilizers. Such fertilizers contain both inorganic plant nutrients, such as nitrogen and phosphorous, and organic materials capable of being broken down to form a humus which contains humic acid, fulvic acid and humin, and is desirable for conditioning the top layer of soil. For example, the humus enhances the capability of the soil to absorb and retain moisture, produces a soft, friable soil which improves penetration of air and water into the root zone and creates an environment for supporting large population of beneficial soil organisms.
The plant nutrient value of such organic materials and wastes usually is quite low, the total amount of inorganic plant nutrients being as low as 1-5% in some cases. Also, the natural biological process for decomposing the organic materials into the desired humus requires a relatively long time. Because of the low plant nutrient value and the time required for the natural decomposition of the organic materials, synthetic inorganic fertilizers are much more widely used. Some of the inorganic materials can be leached from synthetic fertilizer during rain or irrigation. In addition to not being available as to serve as a plant nutrient, the leached inorganic materials can be carried into and pollute waterways.
II. Prior Art
Processes for treating organic materials and wastes to accelerate break down of the organic material and add inorganic nutrients to form a higher analysis fertilizer are known. Wilson U.S. Pat. No. 3,050,383 discloses a process for producing a high analysis granular fertilizer from a low analysis organic waste material, such as sewage sludge and animal manure, by simultaneously admixing with the waste material sulfuric or phosphoric acid and an aqueous ammoniacal solution and tumbling the resulting reaction mass to form granules.
O'Neill et al. U.S. Pat. No. 3,966,450 discloses a process for simultaneously controlling the odor and increasing the plant nutrient value of an animal waste slurry by admixing therewith an aqueous hydrogen peroxide solution, adjusting the pH to 4-8 by adding a mineral acid and mixing the slurry until the animal waste odor is no longer objectionable and ammonia is converted to an ammonium salt.
O'Donnell U.S. Pat. No. 3,942,970 discloses a process for treating sludge filter cake to produce a granular, high nitrogen fertilizer by introducing comminuted, partially dried sludge filter cake into a reactor, adding an acid to decrease the pH to 3-5 and reacting an alkaline N-methylol-urea aqueous prepolymer solution with the partially-dried, acidified sludge, while vigorously mixing the sludge particles to complete the reaction and conversion of the prepolymer, to produce a granular reaction product comprising the condensed polymer and dried sludge.
Trocino U.S. Pat. No. 3,929,446 discloses a process for producing a fertilizer from Douglas fir bark by extracting wax and removing the cork from the bark and then blending a water soluble nutrient, such as urea, ammonium nitrate or super phosphate, with the remaining matrix.
Applicant's earlier patent, Robinson U.S. Pat. No. 4,743,287, discloses a process for producing a granular or slurry fertilizer product from organic materials and wastes by sequentially blending an acid material and a base material with the organic material in a sealed reactor and maintaining the pressure in the reactor up to 30 psi. A reactor capable of withstanding such pressure can be quite expensive to manufacture and maintain operational. It also can be difficult to maintain pressure seals at the material inlet and outlet and the inlets for the acid and base materials.